How to define (and plot) a non-continuous function in R?-CodePudding

Suppose we have the function y = x^2, we could plot this continuous function from x=0 to x=100 like so:

library("ggplot2")
eq = function(x){x^2}
ggplot(data.frame(x=c(1, 100)), aes(x=x))   
  stat_function(fun=eq)  
  theme_void()

Question

But suppose we wish to define a non continuous function, such that, say, it's the same as y=x^2 but there are no values for x between 20 and 30, and 50 and 70. How could we define it?

Context

I'm trying to replace the second line below (eq = function(x){x*x}) with whatever is necessary in order to plot noncontinuous function (i.e. keeping all other code the same).

library("ggplot2")
eq = function(x){x*x} # CHANGE ONLY THIS LINE (IF POSSIBLE)
ggplot(data.frame(x=c(1, 100)), aes(x=x))   
  stat_function(fun=eq)  
  theme_void()

I'll be trying to plot many non continuous functions on the same plot, so I suspect any hacks on the plot itself (e.g. adding elements over the top of the continuous function) would not scale well..

CodePudding user response：

You can just replace the output of your function with NAs for values of x that aren't part of your domain.

library(ggplot2)

eq <- function(x) {
  ans <- x * x
  ans[x >= 20 & x <= 30] <- NA
  ans[x >= 50 & x <= 70] <- NA
  ans
}

ggplot(data.frame(x = c(1, 100)), aes(x))  
  stat_function(fun = eq)  
  theme_void()

^{Created on 2021-12-29 by the reprex package (v2.0.1)}